A light metal workpiece is typically provided in a near net shape which preferably requires a single minimal depth-of-cut chip removing cum finishing operation to arrive at its desired highly smooth final net shape. For the purpose of machining a workpiece to a highly smooth finish, a milling cutter requires minimal runout in general and minimal axial runout in particular attained 'by its cutting inserts being mounted such that their operative front cutting edges lie on a single plane, namely, the workpiece's face plane.
A milling cutting insert of parallelipipedal shape as described in the Applicant's U.S. Pat. No. 5,207,538 to Satran can be disposed in one of two dispositions in both of which it is axially inclined so as to provide suitable axial rake and relief angles. In a first disposition, the insert is respectively axially and radially supported by a single support surface and two spaced apart support surfaces provided by the side walls of an insert receiving pocket such that a long main cutting edge serves as a side cutting edge and a dedicated front cutting edge of a protruding nose-like cutting corner serves as a wiper to wipe a face plane of a workpiece. In a second disposition, the insert is respectively axially and radially supported by two spaced apart support surfaces and a single support surface provided by the side walls of an insert receiving pocket such that an extension of its long main cutting edge is angularly disposed to serve as a wiper to wipe a face plane of a workpiece. In both modes, due to the tolerances in its insert receiving pockets, the milling cutter is unable to wipe a face plane to a highly smooth finish and consequently such a finish is typically achieved by a subsequent grinding operation.
As described in U.S. Pat. No. 2,805,469 , it is known to provide axially inclined insert receiving pockets in a two-piece milling toolholder constituted by a main body on which an annular flange ring, is adapted to be nested on from the rear such that the main body provides the pockets' base support surfaces and radial support surfaces for respectively taking up tangential thrust and radial thrust and the annular flange ring provides the pockets' axial support surfaces for taking up axial thrust. Notwithstanding the detrimental affect on axial runout due to the axial inclination of the base support surface, the annular flange ring requires radially extending notches such that inserts are not axially supported on along their upper side edges which further increases axial runout.